April/May 1980 · Issue 7

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Is Marvin A Nascom 1 Or A Nascom 2?

I have just added 8K ROM BASIC to Marvin, and have come to the conclusion that I am now a Nascom 2 owner, apart from a small problem with my graphics character set, which should soon be corrected. I had designed a board for the Basic chip to go on, in preference to hacking my memory board about. It didn’t quite work, and I am not sure why? If there are any hardware experts reading this, who can tell me what sort of fault would prevent such a board from running a program, but still allow its contents to be tabulated correctly, I should like to hear from them. If the board can be made to work properly, I intend to make the design available to you all, almost free (photo-copying charges only).

In the meantime, if you are thinking of using the EPROM sockets on your memory board for the Basic, and like me do not want to cut the board about, use a 24 pin wire wrap socket to hold the ROM, and bend pins 18, 19, 20 and 21 out sideways. (I hope that you mean the wire wrap socket and not the ROM! –Ed.) Connect these with wire links to the plated through holes nearest to the places mentioned in INMC 5, page 12. Connect a suitable capacitor across pins 12 and 24 of the wire wrap socket, and there you are. (If it gives trouble such as hanging up for no apparent reason, use a National Semiconductors 81LS97 for its buffer.) This does prevent the use of the other three EPROM sockets, I hasten to add.

Sorry there are no useful bits of machine code here this time, but I seem to spend a lot of time either soldering, or wondering what has caused my perfect program to print “?SN Error”. Nothing to do with plum wine, honest......

ROM Graphics Set

  – See page 27.

From V.P. Lipton

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